A check valve is a group arranged in a pipeline to make a medium directionally to flow without backflow, and is used for various pipe networks more and more widely. At present, a check valve mounted at a water outlet of a water pump is capable of automatically realizing pump starting when valve is closed and two-stage closing without any other additional device has many problems in terms of structure and use.
{circle around (1)} A slow closing small valve plate (or called a slow closing cam) is connected with a valve rod through a hinge (or a chain plate) with a sliding chute, there is a free travel, the valve rod cannot completely control the position of the slow closing small valve plate, and in a running process of the valve, the slow closing small valve plate is in an uncontrolled state, and may swing under the disturbance of water flow, so that flow resistance is increased, and an opening state of the valve cannot be externally reflected; and when the small valve plate is not at a completely-opened position under a small-flow or low-pressure working condition, the slow closing small valve plate may be rapidly closed under the action of gravity due to the existence of the free travel when a large valve plate is rapidly closed, so that a slow closing stage of two-stage valve closing exists in name only.
{circle around (2)} An eccentric design of the large valve plate is unreasonable and free of gravity centre check, and the completely closing of the large valve plate requires backflow water, which may cause a phenomenon of collision during valve closing, high backflow, long reversal time of the water pump, high reversal rotating velocity and potential safety hazards; and a metal hard sealing form of a sealing pair is not allowed due to the existence of phenomena of collision and impact.
{circle around (3)} After the whole valve is closed, the valve rod serves as a maximum force applicator, and maximum support reaction on the valve rod forms an included angle with an axial line of the valve rod, so that the valve rod is subjected to radial bending moment, and is easily bent, and a guide bushing of the valve rod is easily squeezed and damaged to cause a failure of the valve rod.
{circle around (4)} Disconnection prevention structures such as locking nuts and split pins are adopted as connecting parts of the slow closing small valve plate (or called the slow closing cam), and since the small valve plate swings under the disturbance of the water flow, the phenomena that the split pins are sheared, the locking nuts are loosened and disconnected and the whole slow closing cam is detached and washed away by water often appear, which makes it impossible to close a slow closing hole.
{circle around (5)} A shape of the large valve plate is inconsistent with a low-flow-resistance drop-shaped streamlined design, and the small valve plate with the free travel may swing under the disturbance of the water flow, so that running water head loss is increased, and the valve is not an energy-saving product.
{circle around (6)} A straight flow type structure is adopted, so that resistance loss is great.
Therefore, the research and development of a novel diaphragm control slider type tilting disc check valve has become a technical problem urgent to be solved.